1. Field of the Invention
This invention relates to a golf ball having improved spin properties, good hitting feel, a satisfactory initial speed, and durability.
2. Prior Art
As the cover material of two-piece golf balls and some wound golf balls, ionomer resins in the form of ethylene-(meth)acrylic acid copolymers are widely used and accepted because of their long-lasting impact resistance and cut resistance. Since the ionomer resins provide hard hitting feel and high hardness as compared with the balata rubber conventionally used as the cover material, golf balls with an ionomer resin cover are said difficult to impart a desired quantity of spin and inferior to control on iron shots.
For improvements in these respects, U.S. Pat. No. 4,884,814 or JP-A 308677/1989 proposes to blend an ionomer resin in the form of an ethylene-(meth)acrylic acid copolymer having a certain spectrum of physical properties with a specific amount of an ethylene-(meth)acrylic acid-(meth)acrylate terpolymer ionomer which is a relatively soft ionomer resin. The soft/hard ionomer blend is used as a golf ball cover. This is a quite effective technique for improving the hitting feel and control of golf balls using a conventional ionomer resin in the form of an ethylene-(meth)acrylic acid copolymer as the cover.
Nevertheless, the golf ball cover of the above-mentioned soft/hard ionomer blend has several problems. Since the cover is softer and has a lower hardness, the cover itself is less repulsive, leading to a golf ball having substantially reduced repulsion. Also the soft ionomer cover allows the ball to receive more spin by an iron shot, which means the increased frictional force between the club face and the cover. Then balls using a hard core such as two-piece solid golf balls have the likelihood that the ball surface be peeled as a consequence of iron shots because the cover surface can be scraped by grooves across the iron club face.